The extra weight the GTC carries over the fixed roof GT barely seems to dim its enthusiasm for reeling in the horizon. The sprint to 60mph takes 4.8 seconds, two tenths longer, and the top speed falls an insignificant 3mph to a still titanic 195mph. However, the Speed version with its 50bhp increase (600bhp instead of 550bhp), launched in 2009, shaves three tenths off its time over the benchmark.

In the standard GTC, there’s little indication that there are two turbochargers working away at all, just a smooth swell of acceleration from idle that really starts to kick as the rev counter passes 3000rpm. All that low down surge makes them feel like incredibly an powerful turbodiesel, but with far more refinement. However, the Speed model is even more impressive – its maximum torque of 553lb-ft (substantially higher than the 479lb-ft in the standard car) is available from 1700-5600rpm.

A feature of the Speed model absent from the standard car is a tuned exhaust note resulting in a deep, powerful burble when accelerating giving the driver a feel-good moment virtually every time more speed is summoned. Paddles behind the wheel give you the option of controlling the smooth-changing six-speed automatic gearbox but with so much pulling power there’s little need to disturb it from Drive.

While the Bentley’s price and on paper performance put it in competition with cars like the Ferrari F430 Spider, it would be unfair to expect the GTC to provide the same sort of hardcore driving thrills as a mid-engined supercar weighing two thirds as much. It’s never going to feel as agile, turn into corners as well, or just plain excite you in quite the same way.

But the GTC is still satisfying to drive on a twisty road when using the W12’s performance. Key to that satisfaction is the massively stiff bodyshell that, even on rough surfaces, seems to resist the shake that blights many converted coupés. Often manufacturers will soften the suspension on convertibles to safeguard this refinement at the expense of some poise but the GTC feel just as accomplished as its hardtop brother, combining great body control with a supple ride and accurate, well-weighted steering.

New for 2009 is the option of fade-resistant carbon ceramic brakes (only in conjunction with 20-inch wheels).